Cleaning of copper and iron salts on marble surfaces

Staining of marble facings by copper and iron salts on pedestals is not only a visual problem but also a risk due to cracking of the surface. From a conservation point of view it is therefore necessary to find a method which is capable of removing iron and copper stains without destroying the marble surface. For this purpose chemical cleaning with ligands coordinating to copper (II) and iron (III) but with low affinity towards calcium and magnesium ions will be tried.